Espressif Systems ESP32-WROVER-E User Manual page 7

2. Pin Definitions
Name No.
IO19 31
NC 32
IO21 33
RXD0 34
TXD0 35
IO22 36
IO23 37
GND 38
Notice:
* GPIO6 to GPIO11 are connected to the SPI flash integrated on the module and are not connected out.
2.3 Strapping Pins
ESP32 has five strapping pins, which can be seen in Chapter
• MTDI
• GPIO0
• GPIO2
• MTDO
• GPIO5
Software can read the values of these five bits from register "GPIO_STRAPPING".
During the chip's system reset release (power-on-reset, RTC watchdog reset and brownout reset), the latches
of the strapping pins sample the voltage level as strapping bits of "0" or "1", and hold these bits until the chip
is powered down or shut down. The strapping bits configure the device's boot mode, the operating voltage of
VDD_SDIO and other initial system settings.
Each strapping pin is connected to its internal pull-up/pull-down during the chip reset. Consequently, if a
strapping pin is unconnected or the connected external circuit is high-impedance, the internal weak pull-up/pull-
down will determine the default input level of the strapping pins.
To change the strapping bit values, users can apply the external pull-down/pull-up resistances, or use the host
MCU's GPIOs to control the voltage level of these pins when powering on ESP32.
After reset release, the strapping pins work as normal-function pins.
Refer to Table 4 for a detailed boot-mode configuration by strapping pins.
Pin Default
MTDI Pull-down
Type Function
I/O GPIO19, VSPIQ, U0CTS, EMAC_TXD0
- -
I/O GPIO21, VSPIHD, EMAC_TX_EN
I/O GPIO3, U0RXD, CLK_OUT2
I/O GPIO1, U0TXD, CLK_OUT3, EMAC_RXD2
I/O GPIO22, VSPIWP, U0RTS, EMAC_TXD1
I/O GPIO23, VSPID, HS1_STROBE
P Ground
Table 4: Strapping Pins
Voltage of Internal LDO
3.3 V
0
6 Schematics:
(VDD_SDIO)
5
1.8 V
1